Cutting tools employing a resilient clamping mechanism for clamping cutting inserts are generally of relatively narrow thickness. For example, cutting operations such as grooving and parting off can be performed by a cutting insert retained in an insert pocket located between the clamping surfaces of upper and lower jaws of a relatively narrow holder blade. The holder blade is, in turn, generally clamped in a blade-retaining block. The holder blade is generally provided with a suitably designed opening, in the vicinity of the insert pocket whereby a relatively narrow bridging portion is formed enabling a limited degree of resilient displacement of one of the holder blade's jaws relative to the other. Generally, the lower jaw is rigid and the upper jaw is resiliently displaceable. The opening can be of the form of an aperture, or a slot, or a slot terminating in an aperture. Examples of such cutting tools are disclosed in U.S. Pat. No. 3,785,021 and U.S. Pat. No. 4,580,930. A rotary slot-cutting tool employing a resilient insert clamping mechanism is disclosed in U.S. Pat. No. 5,059,068. The cutter body is disc-shaped and of relatively narrow thickness, with cutting insert pockets located around its periphery. As with the holder blade, an insert pocket has two jaws between which an insert is clamped by means of the resilient force resulting from the bending of the clamping jaw.
Whether the cutting tool is a holder blade or a rotary slot cutting tool, the bending of the clamping jaw is obtained by manufacturing the insert pocket such that the distance between the clamping surfaces of the jaws is smaller than the height of the portion of the insert located between the clamping surfaces. Consequently, when an insert is located in the insert pocket, the clamping jaw is held in a bent position creating an elastic force by means of which the insert is clamped in position.
A well-known disadvantage of this form of clamping mechanism is the instability of the clamped cutting insert in certain cutting tools and under certain cutting conditions. In rotary slot cutting tools, each individual cutting insert intermittently makes contact with a workpiece as the tool rotates about its axis of rotation. As a result a cutting insert suffers a blow each time it hits the workpiece and is likely to be displaced due to a diminishing of the clamping force. If only some of the inserts are so displaced, or they are displaced by different radial distances, then the undisplaced ones, or the less displaced ones, will stop participating in the slotting operation causing uneven wear of the inserts. Instability of the cutting insert also arises in the use of inserts retained in holder blades in, for example, grooving operations. When the holder blade is pulled out from a completed groove the insert can be accidentally be pulled out of the holder blade.
A solution to this problem is proposed in U.S. Pat. No. 5,743,680 which discloses a specially designed cutting insert and a correspondingly specially designed insert pocket in the holder blade. Similarly, a solution to the problem of insert instability in rotary slot cutting tools is proposed in U.S. Pat. No. 5,059,068 in which specially designed inserts and correspondingly specially designed insert pockets in the cutter body are disclosed.
It is the object of the present invention to provide a resilient clamping mechanism for insert, which, inter alia, overcomes the aforementioned problem of possible displacement of an insert in a reliable and novel manner.